Man charged over assault at party gatecrash

An 18-year-old man has been charged over the serious assault of a young Sydney partygoer last month.

Shortly after 11.30pm on January 11, a group of people attempted to gatecrash an 18th birthday party at a home in Forestville, on Sydney's north shore.

Following a physical altercation between the group and those celebrating the birthday, police allege an 18-year-old man climbed over the rear fence on to the roof of a garden shed, before throwing objects, including metal rods, at the partygoers.

Liam Knight, 17, suffered serious head injuries after a metal rod pierced his skull. He was rushed to Royal North Shore Hospital where he remained in an induced coma for almost a fortnight.